Happy feast of St Dunstan!
St Dunstan's feast day, as with the principal feasts of most saints in the calendar, is celebrated on the day of his death (19 May) in 988. Medieval Latin saints' lives sometimes use the term natalicia in coelo ('birth into heaven'), a good expression for the passage from this life into the next as part of the 'communion of saints' [Apostles' Creed, see For All the Saints pp.11 ff.] and 'great cloud of witnesses' [Hebrews 12:1] of every age.
More about the death of St Dunstan from Dr Eleanor Parker's A Clerk of Oxford blog, here.